Synthesis And Recognition Properties Of Schiff Bases Fluorescent Probes

Objective:To explore the preparation of simple and highly selective recognition of transition metal ions Schiff base small molecule fluorescent probes,and applied to the actual sample transition metal ion content determination.Methods:A novel Schiff base fluorescent probe L₁ was prepared by substitution and condensation reacctions using 4-bromo-1,8-naphthalimide,hydrazine hydrate,4-?2-aminoethyl?-morpholine and salicylaldehyde;4-tert-butyl-2,6-dicarboxyphenol and nicotinic acid hydrazide were used as raw materials obtained by one-step condensation of fluorescent probe L₂.The structures and compositions of L₁ and L₂were characterized by ¹H NMR,¹³C NMR,FT-IR,HR-MS and other analytical techniques.Fluorescence spectrophotometry and UV-Vis spectrophotometry were used to study the recognition performances of such two probes to common metal ion and anion in laboratory,¹H NMR titration,HR-MS and EDTA titration experiments confirmed its recognition mechanism.Results:Two novel Schiff-base fluorescent probes were successfully synthesized,the common laboratory identification of anion and cation performance studies have shown that:?1?L₁ can selectively recognize Cu²⁺by fluorescence quenching in a mixed solvent of anhydrous ethanol and Tris-HCl?1/1,v/v,pH=7.4?,and can be observed under the naked eye with 365nm UV lamp possessing fluorescence quenching behavior.The detection limit of Cu²⁺was 0.047?mol/L₁,There is a good linear relationship between the concentration of Cu²⁺and the fluorescence intensity of probe L₁ in the concentration range of?2.0-9.0?mol/L?.The average labeled amount of Cu²⁺for the fluorescent probe was 106.5%,which could be applied to the determination of Cu²⁺in real water sample.?2?L₂ selectively recognizes Ca²⁺,Zn²⁺,Cu²⁺and Co²⁺in a mixed solvent of absolute ethanol and Tris-HCl?9/1,v/v,pH=7.4?.Among them,Ca²⁺combined with L₂ could be observed with naked eye under365nm UV lamp,which meant that it had the special response to fluorescence spectrum.In addition,the detection limits of L₂ for Ca²⁺,Zn²⁺,Cu²⁺and Co²⁺were1.43×10^-7 mol/L,1.12×10^-5 mol/L,3.56×10^-77 mol/L and 3.39×10^-77 mol/L respectively.The concentration range of Ca²⁺in the range of 2-9?mol/L showed a good linear relationship with fluorescence intensity,the absorbance of Zn²⁺,Cu²⁺,and Co²⁺in the concentration range of 0-14?mol/L,6-18?mol/L,and 2-12?mol/L showed a good linear relationship.With regard to the average labeled amount of each ion in the drug,they were Ca²⁺?98.2%??Zn²⁺?87.0%??Cu²⁺?94.1%?and Co²⁺?96.0%?respectively,The recoveries of water samples were Ca²⁺?98.9%?94.2%?97.1%?,Zn²⁺?98.1%?101.9%?98.1%?,Cu²⁺?93.8%?91.6%?93.8%?and Co²⁺?91.9%?98.2%?101.0%?,respectively.Conclusion:Preparation of two new Schiff base fluorescent probes can detect and quantify Cu²⁺,Ca²⁺,Zn²⁺and Co²⁺at low detection limit,Among them,the sensor L₂has the function of multi-function recognition of various ions.